The invention relates to an apparatus for regulating the fuel air ratio of the combustible mixture fed to the cylinders of an internal combustion engine. More particularly, the invention relates to a regulator in which the fuel quantity is adjusted arbitrarily while the airflow rate is measured and causes a fuel throttle to limit the amount of fuel provided to the engine. The apparatus compares the fuel quantity provided to the engine with the correct quantity admitted by the air-flow related metering system and corrects the delivered fuel quantity accordingly. Known in the art is an apparatus in which the airflow rate to the engine is set arbitrarily while a throttling member in the fuel supply line meters out the correct fuel and where a differential pressure valve controls a second throttle for correcting any deviation of the differential pressure accross the metering aperture.
Also known in the art is an apparatus in which the injected fuel quantity is changed arbitrarily and where any change in the differential pressure across the fuel metering aperture which is controlled by the airflow rate meter causes a differential pressure valve to throttle the airflow through the induction tube. Accordingly, the changed airflow rate corrects the previously detected deviation of the differential pressure and thus maintains a desired fuel-air ratio of the combustible mixture.
The known apparatus is distinguished by requiring a throttling device for the aspirated air as well as an airflow metering device. It is well known, however, that throttling of the air passages in an engine results in a disadvantageous reduction of the power which the engine is capable of producing. Furthermore, in the known apparatus, the fuel-air ratio can be corrected only after the disturbance caused by the change in fuel quantity has traveled over a relatively long control path which is thus subject to a large number of disturbing influences. In particular, a change in the differential pressure first causes a control pressure for the actuation of the air throttling mechanism as a consequence of which the airflow rate changes and causes the airflow rate meter to alter the fuel supply via a throttle operated thereby. The various transfers may introduce errors which falsify the fuel-air ratio.